A goniometer is a device for measuring or setting angles. Prior art goniometers have utilized a number of principles to determine angles. Reference may be had, for example, to The Biomedical Engineering Handbook (Joseph D. Bronzino Ed., CRC Press LLC, 1995) pages 2177-2182.
Prior art goniometer designs include the following categories; Universal, Arthroidial, Fluid, Pendulum, Myrin OB, and Electrogoniometer.
The Universal Goniometer comprises a protractor-like measuring device with one movable arm and one stationary arm. The two arms are superimposed on the rays of the angle, and the measurement may be read on the protractor. Often, several goniometers of different sizes are required to measure different digits (i.e. a knee versus a finger). Additionally, the increments on the protractor limit the sensitivity of the measurement to the gradations on the instrument. The placement of the arms is also a source of error, as it is difficult to properly align relatively small arms parallel to a large extremity. Providing longer arms on the device may compensate, but this negatively impacts the portability of the device. Reference may be had, for example, to The Biomedical Engineering Handbook (Joseph D. Bronzino Ed., CRC Press LLC, 1995) page 2181.
The Arthroidial goniometer is a single protractor, similar to the Universal goniometer, but lacking arms. These instruments likewise suffer the same drawbacks. Reference may be had, for example, to The Biomedical Engineering Handbook (Joseph D. Bronzino Ed., CRC Press LLC, 1995) page 2181.
Fluid and Pendulum Goniometers utilize gravity to aid in measuring angles. Fluid goniometers contain a fluid-filled channel with an air bubble that moves as the device changes its angle relative to the gravitational plane. Likewise, Pendulum goniometers contain a pendulum for detecting angular changes. Such goniometers are often more accurate than their universal counterparts, but are additionally more expensive. Reference may be had, for example, to The Biomedical Engineering Handbook (Joseph D. Bronzino Ed., CRC Press LLC, 1995) page 2181.
Myrin Goniometers exploit a combination of gravity sensing devices and magnetic field sensing devices that respond to the Earth's magnetic field. These goniometers are often bulky and useless for measuring the angles associated with small joints, such as the fingers. They additionally suffer to electromagnetic interference. Reference may be had, for example, to The Biomedical Engineering Handbook (Joseph D. Bronzino Ed., CRC Press LLC, 1995) page 2181.
Electrogoniometers are physically strapped to the proximal and distal portions of the joint to be measured. These devices are inherently cumbersome and expensive. Each electrogoniometer is designed for specific body parts and they are typically used only as pieces of laboratory equipment. Reference may be had, for example, to The Biomedical Engineering Handbook (Joseph D. Bronzino Ed., CRC Press LLC, 1995) page 2181.
By way of further illustration, U.S. Pat. No. 3,634,838 discloses a goniometer arrangement that allows for the digital display of the measured angle. Such a digital display circumvents the difficulties associated with protractor measurements, such as being limited to the increments marked on the protractor.
U.S. Pat. No. 4,665,928 of Linial teaches the use of pendulum goniometers to determine angles on a living person. This patent also discloses the use of potentiometers to digitize the measurement, thus avoid protractor-like measurements.
U.S. Pat. No. 4,883,069 discloses an electrogoniometer that physically attaches to a joint through the use of straps.
U.S. Pat. No. 5,189,799 discloses a goniometer comprised of a single laser to determine the angle of a geographic feature.
U.S. Pat. No. 5,832,422 discloses a hand-held measuring device that is capable of measuring angles. The device tracks the angle the device is moved as it proceeds from a first position to a second position.
U.S. Pat. No. 6,428,490 discloses a series of resistive bend sensors that may be built into a garment to measure the range of motion for computer animation, for example. Such a suit would be undesirable for simple medical measurements due to the size of the device, its complexity, and its cost.
In spite of the substantial amount of prior art disclosing goniometers, these prior art goniometers suffer from a number of disadvantages. Many of the prior art instruments utilize manual, as opposed to digital, measurements, which inherently limit the precision of the measurements to the gradations on the protractor. Additionally, many prior art angle-measuring devices must use long arms in order to accurately visualize the rays of the angle to be measured. These long arms make these devices cumbersome and unsuitable for use with small joints. Additionally, many of the prior art goniometers are expensive, and difficult to transport, diminishing their usefulness as everyday instruments.
The instant invention seeks to overcome all of these disadvantages and provide a measuring device that utilizes light beams in place of traditional goniometer arms. The longer the arms of a traditional goniometer, the easier it becomes to estimate the position of the ray of the angle to be measured. However, longer arms make the device less portable. The instant invention replaces the physical arms of prior art goniometers with a beam of light. The long light beams mimic the advantageous function of long arms without requiring a large volume of space. Specifically, one light beam may be aligned along the length of one section of an extremity (i.e. lower leg), while the second light beam may be aligned along the length of a second section of the same extremity (i.e. upper leg). The goniometer may read the angle between the two beams throughout the flexion and extension of the extremity. In this manner, a range of motion may be determined.
It is an object of this invention to provide a lightweight, portable, hand-held goniometer.
It is another object of this invention to provide a goniometer that can easily, and accurately estimate the position of the two rays of an angle.
It is yet another object of this invention to provide a goniometer that digitally displays an angle measurement with a high degree of precision.
It is another object of this invention to provide a goniometer that is useful on both large joints and small joints.